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location  University of Copenhagen  
age  29  
visits  member for  5 years 
seen  4 hours ago  
stats  profile views  8,307 
1d

comment 
cohomology of a variation of wreath product
Consider the maps $(z_1,\ldots,z_n,z_{\sigma(1)}, \ldots,z_{\sigma(n)}) \mapsto (tz_1,\ldots,tz_n,tz_{\sigma(1)}, \ldots,tz_{\sigma(n)})$ for $t \in [0,1]$: this is a homotopy between the identity map and the constant map $(0,0,\ldots,0)$. 
2d

comment 
cohomology of a variation of wreath product
Are you sure you're asking the question you intended to ask? The space you wrote down is obviously contractible. You could insist that all $z_i$ are distinct but in this case you would obtain $n!$ copies of the usual configuration space of $n$ ordered points in $\mathbf C$. 
2d

reviewed  Close Diffusion Equation 
2d

reviewed  Close How to calculate a sequence in Maple 
Nov 18 
awarded  Nice Answer 
Nov 16 
awarded  Good Answer 
Nov 13 
awarded  Enlightened 
Nov 13 
awarded  Nice Answer 
Nov 12 
comment 
Framed version of braided monoidal category
You're right, they form a nonsymmetric operad. By the way, I think there are some things you might find useful in Nathalie Wahl's Ph.D. thesis. 
Nov 12 
comment 
Gerbes and Stacks
I don't really understand you so at least one of us is confused. The fiber over a point of $U_i$ is a groupoid with one object and morphism set $BGL(1)$. 
Nov 12 
answered  Framed version of braided monoidal category 
Nov 12 
answered  Gerbes and Stacks 
Nov 11 
comment 
List of Classifying Spaces and Covers
...and even if you find the previous example too silly, allowing yourself to work with stacks does give you several natural examples, like $\mathrm{SL}(2,\mathbf Z)$ acting on the upper half plane. 
Nov 11 
comment 
List of Classifying Spaces and Covers
Here's a really dumb nonanswer (dumb enough that I only make it a comment), but sometimes I find it useful to think along these lines. Namely, if you permit yourself to think about topological stacks instead of topological spaces, you can take $EG = \ast$ (a single point) and $BG = [\ast/G]$ ($G$ any group). This is the universal and minimal choice of classifying space. 
Nov 11 
comment 
Synthetic vs. classical differential geometry
There's an interesting recent book by Paugam that you might like (although I've only looked briefly at a few chapters), "Towards the Mathematics of Quantum Field Theory". The goal of his book is to formulate QFT mathematically in the most "correct" way possible, which for him means in terms of SDG, diffeological spaces, and homotopical algebra. 
Nov 10 
comment 
The properness of a submersion
I don't think this completely answers the question. Consider e.g. $\mathbf R\setminus \{0\} \sqcup \{0\}$ with its natural map to $\mathbf R$, which is a nonproper map with compact connected fibers. To rule out a silly counterexample like this it seems one should use the submersion hypothesis (which your argument doesn't). 
Nov 8 
awarded  Nice Question 
Nov 8 
asked  What's the dimension of the space of CM cusp forms? 
Nov 6 
answered  why are motives more serious than “naive” motives? 
Nov 4 
accepted  Which mapping class group representations come from algebraic geometry? 